Differential gears permit the relative rotation of two shafts driven by a third drive shaft, the sum of the rotation rates of the driven shafts being constant. Differential gears typically comprise a drive shaft which rotates a cage containing a planetary bevel wheel or wheels which mesh with two bevel wheels, one on each of the driven shafts. The meshed bevel wheels cause the sum of the rotation rates of the driven shafts to be constant, although they may rotate at different rates.
Such differential gears are widely used, for example in cars, but the manufacture of the cage and bevel wheels is expensive and places a price barrier upon goods containing differential gears.
The present invention overcomes the problems of the prior art, and provides a simple, convenient, less expensive differential gear.